Carbon-Fiber-Reinforced PEEK Composite Material For Medical Applications

Composite Material in the Medical Field

Question:

Write a Research Paper on a Composite Materials of your Choice used in Medical Application.

According to Goodman et al. (2011), a composite material refers to a combination of two or more materials that are of different composition, physical property, and morphology. These materials are often combined on a microscopic scale. Depending on the constituent properties, composites are in many cases designed to (or “intending to”) producing materials with materials aimed at fulfilling specific mechanical, physical, or chemical requirements. As a result, Hofmann (2016)  points out that the use of composite materials have progressively increased for the past 40 years and have many uses in the automotive, aeronautic, medical, and naval fields among other industries. Consequently, different composite biomaterials have been tested and studied for use in the medical field and are often commercialized for their advantages of the traditional composite materials that were used before.

In the medical field, most human tissues such as skin, bones, tendons, teeth, and ligament are composites made up of single constituents whose distribution, morphology, amount, and properties are the major determinants of the final behavior of the resulting organ or tissue according to Paknikar and Kumbhar (2015). The same study denotes that human-made composite materials can as well be used in making prostheses that are used to mimic these biological tissues with the aim of ensuring thy match their mechanical behavior and restore the mechanical functions of the body tissues that have been damaged. This paper presents the history, structure and synthesis, mechanical properties, possible uses, as well as pros and cons of the carbon-fiber-reinforced,  peek (CFR-PEEK) composite material whose use have been studied, tested, and proven fit for medical purposes.

Carbon Fiber, a polymer that is also known as a graphite fiber, is a very strong material and light in weight. Though stiffer than steel, its light weight makes it suitable for use as a raw material in the manufacturing of other materials (Garry, 2013). The composite material was discovered back in 1879 by Edison Thomas. The scientist backed bamboo silvers and cotton threads at high temperature carbonizing them into a fiber filament of all-carbon. His invention led to the use of high-performance carbon fibers in 1958 in Cleveland. CF-PEEK was then introduced as a matrix where long and short PEEK fibers were used as the composite matrix to ensure the end product had the qualities of both fibers. Despite the fact that they were inefficient, the fibers contained approximately 20% carbon with low stiffness and strength properties. However, the carbon fiber’s strength potential was realized in 1963 through a new manufacturing process at British research center (David et al., 2014).

In the medical field, carbon-fiber-reinforced peek materials range from large scale components such as x-ray application materials to most invisible bolts internally used to support the bones in the body according to Paknikar and Kumbhar (2015). CFR-PEEK materials have for a long time been adopted for use in the medical field in different facets. They are widely used in the orthopedic processes mainly for bone crafts, bone cementing, hip joint replacement, and in the fixation of the bone plates in the body. Hofmann (2016) points out that CFR-PEEK can be fabricated with tensile strength or stiffness in the capability of the bone they replace in the body. As a result, the materials are successfully finding their way into the medical devices as implants to replace the internal body organs and tissues.

History of Carbon Fiber and CFR-PEEK Composite Material

Historically, many challenges have been faced by implant designers in achieving acceptance from different regulatory agencies globally. However, the uses of carbon-fiber-reinforced peeks are on the rise as a result of technological advancements and innovations. New medical applications and composite materials are gaining popularity and approval in many parts of the US food and drug administration (Garry, 2013). CFR-PEEK are used in the formulation of bone growths for implants such as temporary bone supports and bone screws mainly adopted in the orthopedic repairs. These materials have been adopted for use in the bioresorbable polymers that can safely break down and be absorbed by the body in the rebuilding process of the bone.

In the medical industry, the first synthesis requirement is a performance parameter indicating the relative merits of different designs of CFR-PEEK with the primary knowledge that the growth and micro-motion of bones can be used for different purposes in a clinical view. What follows is a finite element code that determines the strains in the bone used as essential parameters in evaluating the performance of the carbon fiber. The CF-PEEK composite is manufactured by the use of a hybrid fabric composing of PEEK and carbon fiber as a matrix that is then modified and treated by low temperature and oxygen plasma. The process is then followed by X-ray photoelectron spectroscopy, Fourier transformation attenuated total reflection infrared spectroscopy (FTIR-ATR), and Scanning Electron Microscopy (SEM) that are essential I relating the functionality and roughness of the carbon fiber surface with the PEEK interfacial adhesion strength.  The plasma treatment is aimed at increasing the roughness of the carbon fiber surface while the prolonged treatment results into the smoothing.

Figure 1: The structure of carbon

According to Duraccio, Mussano, and Faga (2015), the structural properties of a composite material are determined by the length, volume, and alignment of the carbon fiber it contains. Apart from being strong, carbon fibers have high tensile strength and stiffness but with low weight. It also has a high chemical resistance and is often tolerant to high temperature and excessive heat but with a low thermal expansion as denoted by Garry (2013).

According to Cano and Guilemany (2016), the mechanical property of a composite material can be determined by the mechanical properties of CFR-PEEK. Carbon fibers consist of strong and thin crystalline carbon filaments for the strengthening of other materials. David et al. (2014) denote that the fibers can be thinner than the human hair but gets its strength when the fibers are twisted and laid over a coated and molded into plastics or resin. For these mechanical properties, carbon fiber is adapted for use not only in the medical field but many industries such as the military, automotive, and aerospace.

There are two main forms of carbon fiber incorporation used in composites for medical applications. Short CFR-PEEKs that consist of short carbon fibers randomly aligned and are mostly less than 0.4 mm, used as producers of the homogeneous material property for the implant. Long CFR-PEEK consists of carbon fibers essentially running the entire width of most composite materials. The long CFR-PEEK has a tensile strength that is greater than 2000 Mpa when compared to the 170 Mpa which is of the short carbon fiber (Aspenberg, 2014). As a result, their controlled alignment of these carbon fibers hence helps in providing a broad range of anisotropic properties that can be controlled for specific functions depending on there the composite material that needs to be made and the use. 

Uses of CFR-PEEK in the Medical Field

Figure 2: A summary of the mechanical nature of carbon-fiber-reinforced peek

Ajioka et al. (2016) denote that carbon-fiber-reinforced peek material is engineered to produce a varying degree of stiffness and strength based on the number and orientation of the carbon fibers used. It is hence easier to help the manufacturer match the elasticity of the bone to be replaced with the composite implant material that will be fixed. On the other hand, Paknikar and Kumbhar (2015) also denotes that using carbon fibers as composite materials is easier since, before their innovations, manufacturers were facing challenges from modulus mismatch of the then used metal implants. For instance, the mismatch was often producing stress shielding; alter loading, and a periprosthetic bone remodeling process that was often detrimental.

Commercially available carbon fiber composite materials have been tested in several ways for fatigue cycles but have always proven to be effective and resistant. Nayeri (2014) denotes that the average strength for a 4.5mm implant plate is 19.1 Newton meters while that of a similar 4.5mm stainless steel compression plate is 17.8 Newton meters. The bending strength of available 10-mm CFR-PEEK is averagely 80.3 Nm, while an 11-mm titanium tibial plate bending strength is 43 Nm. This has proven that the testing for wear debris of the implants is significantly lower than the wear debris strength of titanium plates made from the steel as pointed out by Goodman et al. (2011). The same study denotes that the healing and fracture reduction are available for a standard radiograph. The absence of both MRI and computed tomography means that CFR-PEEK for the composite implants has applications for infections, spine, and for oncologic cases.

Even though there are several advantages of using the carbon-fiber-reinforced peek composite implants for medical reasons, there are also some specific disadvantages. For instance, they cannot be contoured hence making their use in fracture fixation limited to straight diaphyseal hence calling for a specific locking screw technique anatomically designed for the specific fracture Utech and Boccaccini (2016). At the same time, stiffness can be beneficial to the receiver, but the too much flexibility is as well dangerous as it can lead to pseudarthrosis. The increased fatigue strength of the implants helps in decreasing any possible risk to fatigue failure. However, the radiolucent nature of the carbon-fiber-reinforced peek used in the manufacturing of the implants precludes directly hence visualizes radiography.

Possible uses of Composite Implant

In his study, Hofmann (2016) denotes that all biomaterial composites intended for use in the body of any living organism have to meet certain conditions, regulatory requirements, and criteria. These include;

• The material should not release any harmful components into the living system of the organism
• Must be biocompatible such as tissue or blood compatible, nontoxic, or non-carcinogenic
• The physical and mechanical properties of the material such as durability, stability, and elasticity must be suitable and appropriate for the intended application.
• The mechanical properties of the material have to last for the projected life of the implant or the medical device
• A sterilizable material by a standard method

Carbon-fiber-reinforced peek have found a wide application and use in different facets of the medical sectors. These include bone cementing, bone grafting, hip joint replacements, bone fixating plating, and other forms of bone replacements (Asghari et al. 2017). In the manufacturing and design of prosthetic composite implants used for the replacement of the central bone and the combined joint, the primary objective is often to arrive at an implant with a higher bone growth stimulus but slightly lower that the titanium alloys implants that are currently used (Egger et al. 2017). From the CFR-PEEK innovations, patients can easily get access to rapid and easier proper implant fixation and bone replacement. Achieving these objectives requires the synthesis and structure of the composite implants to consist of three primary elements.

Challenges of CFR-PEEK Incorporation in Implants

In his study, Soboyejo (2017) points out that CFR-PEEK includes bio-glass-ceramic, xenograft, and allografts often used in joint replacements and tissue engineering. They are often made of different layers of long and short carbon fibers; the final product often combines the properties of both the materials used. The resulting product is often mechanically strong but lightweight at the same time. Saleh (2016) also denotes that the materials have low density and can easily resist corrosion. The use of composite body implants has several advantages when compared to the metallic devices that were used before their inventions. It modules if elasticity and fatigue strength makes the CFR-PEEK an ideal composite implant material for bones plates and nails.

The disposal of CF-PEEK is becoming a major issue since the different carbon fiber reinforced composite materials are reaching the end of their live services. According to Schinner, and Brandt (2011), over 27 000 tons of CF-PEEK have produced annually. As a result, grinding up the waste material and sending it to landfills or disposing of it through incineration has little appeal to the environment since it is non-biodegradable.  With global warming and climate change policies affecting every global industry, incineration is not the best method of disposal of the material as it will lead to the production of greenhouse gasses as well as smoke, thus leading to pollution. Disposal into landfills also reduces the aesthetic value of the environment turning the areas into wastelands and creating environments for disease-predisposing factors such as stagnant water collection points for mosquito and bilharzia breeding when it rains. As a result, different recycling methods such as pyrolysis have been adopted that strips away the epoxy resin from the fibers while leaving the original properties undamaged.

Conclusion

The medical industry is driven and guided by the demands of the medical profession that seeks constant improvements and device innovations for better medical care. Consequently, different composite biomaterials have been tested and studied for use in the medical field and are often commercialized for their advantages of the traditional composite materials that were used before. Carbon fibers have found a wide application and use in different facets of the medical sectors. These include bone cementing, bone grafting, hip joint replacements, bone fixating plating, and other forms of bone replacements.

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